The impact of multiple sclerosis relapses on worsening over the long term; insights in the treatment era

Relapses of multiple sclerosis (MS) are the clinical manifestations of inflammatory events involving eloquent anatomical structures within the central nervous system. Relapses are associated with worsening disability of MS patients in both early and later disease, even after progressive features are seen. The impact of relapses on the long-term course of the disease is now being realized as a generation of treated patients is now elderly. New MRI brain lesions can be viewed as a radiologic manifestation of acute inflammation and are associated with similar prognostic value. The complex relationship between clinical relapse activity and later slow progressive worsening remains incompletely understood, however, there is increasing biological plausibility for a causative association between relapse activity and lifelong disability.

Multiple sclerosis relapses contribute to long-term disability

BACKGROUND

Treatments affect both relapse-related disability and short-term disability change, but measurements of their impact on long-term outcomes remain a challenge.

OBJECTIVE

To ascertain the contribution of relapse-associated disability to overall disability in relapse-onset multiple sclerosis (RMS) using long-term data collected in our clinic.

MATERIALS AND METHODS

Retrospective study of a cohort of newly diagnosed patients with RMS, (n = 176) was undertaken, measuring all confirmed changes in disability up to 15 years after onset. Worsening was assessed yearly and in 5-year epochs and was attributed to either relapse (RW) or slow progression (PW).

RESULTS

At data lock, 139/176 (81%) of patients were still actively followed, with Expanded Disability Status Scale (EDSS) available for 10 years post-onset in 145/176 (82%) patients and 15 years post-onset EDSS in 83 patients (mean follow-up entire group 12.7 years post-onset). RW accounted for a large amount of worsening seen in the first 15 years of RMS. RW was less frequent over time, but accounted for most EDSS changes in the first decade of MS (167/267, 63% of EDSS changes), and remained important even in years 11-15 (17/50, 34% of EDSS changes). Median change in disability due to RW vs PW was similar over the entire 15 years.

CONCLUSIONS

Worsening of treated MS was associated with relapses in many RMS patients throughout the first 15 years after onset, suggesting an opportunity for long-term benefit through relapse reduction.